Safety electrical connector



May 19, 1970 B. DEGAETANO 3,513,435

SAFETY ELECTRICAL CONNECTOR Filed Nov. 13, 1968 INVENTOR. BEN DEGAETANO.

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United States Patent 3,513,435 SAFETY ELECTRICAL CONNECTOR Ben Degaetano, Armonk, N.Y., assignor to Continental Research & Development Ltd., Toronto, Ontario, Canada, a company of Canada Filed Nov. 13, 1968, Ser. No. 775,354 Int. Cl. H011 13/44 U.S. Cl. 33942 12 Claims ABSTRACT OF THE DISCLOSURE An improved electrical plug having insulating sleeves slidably mounted on each metal prong and adapted to be displaced into the plug housing when the prongs are par tially or completely inserted into a receptacle. The plug is provided With resilient restraining means which serve to maintain the inner ends of the sleeves within the plug housing but which, by virtue of their resilience, permit the sleeves to be inserted into the housing by driving them along the prongs during the manufacturing assembly of the plug.

BACKGROUND OF THE INVENTION The present invention relates to electrical connectors having electrode prongs and relates more particularly to electrical connectors having a construction which reduces the risk of electrical shock due to accidental contact with the electrode prongs.

Electrical connectors having projecting electrode prongs are well known and, merely by way of example, mention may be made of domestic electrical plugs which are generally provided with two or three electrode prongs. Such electrical connectors or plugs are frequently manufactured by moulding operations using thermoplastic and electrically-insulated composition. In this technique, the electrode prongs with their electrical leads secured thereto are supported in the mould before the body of the plug is moulded therearound. This technique permits a high speed and relatively inexpensive manufacturing operation.

When an electrical plug is inserted into a socket, the prongs are electrified as soon as they come into contact with the conducting members inside the socket. At the time when the prongs become electrified, the plug is not generally fully inserted into the socket and it is possible, therefore, to obtain an electrical shock by accidentally touching the exposed parts of the prongs.

It has previously been suggested that such danger of accidental contact with an electrified electrode prong might be avoided by the provision of retractable insulating sleeves surrounding the prongs. Such previous proposals have, however, called for the incorporation of relatively complex mechanisms within the plugs and consequently it has not previously been possible to manufacture such plugs by high speed moulding techniques.

It is accordingly a principal object of the present invention to provide a novel electrical connector with at least one electrode prong projecting therefrom, such as a domestic electrical plug, which connector is provided with a retractable insulating sleeve around its electrode prong to avoid the aforementioned danger of accidental contact with the electrified electrode prong.

It is a further object of the present invention to provide "ice such a connector having a retractable insulating sleeve around its electrode prong with a construction which permits the high speed manufacture of the connectors.

It is yet another object of the present invention to provide a novel method for the manufacture of an electrical connector having at least one electrode prong with a retractable insulating sleeve around said prong.

- SUMMARY OF THE INVENTION These and other objects are achieved in accordance with the invention by the provision of an electrical connector comprising a housing with at least one electrode prong projecting therefrom, an electrically-insulating sleeve surrounding and slidably mounted on said prong, having an inner end and an outer end and adapted to be displaced into said housing by the application of pressure to said outer end of said sleeve, spring means disposed within said housing and acting on said sleeve to urge said sleeve out of said housing along said prong, and restraining means normally serving to prevent said inner end of said sleeve passing out of said housing but said restraining means being sufiiciently resilient to permit said sleeve to be driven along said prong to introduce said inner end of said sleeve into said housing during manufacturing assembly of said connector.

A particularly useful construction for an electrical connector in accordance with the invention has a housing with an opening through which said electrode prong and said insulating sleeve project. The inner end of the sleeve is normally prevented from passing out of the housing by engagement of an outwardly projecting member secured to the insulating sleeve at or in proximity to the inner end of the sleeve with said housing.

As previously indicated, an electrical connector according to the invention is provided with restraining means which normally prevent the inner end of the insulating sleeve passing out of the housing. Such restraining means are, however, in accordance with an essential feature of the present invention provided in such a manner that the inner end of the sleeve may be introduced into the connector housing during the manufacturing assembly of the connector. This result is obtained by the use of restraining means which are sufiiciently resilient to permit such insertion of the sleeve into the housing.

When the restraining means is formedas an outwardly projecting member at or in proximity to the inner end of the sleeve, this outwardly projecting member itself may be resilient so as to permit, by its temporary deformation, the inner end of the sleeve and the outwardly projecting member to be inserted into the housing through the aforementioned opening. Alternatively, the housing may be formed so as to be resilient in an area adjacent the opening through which the prong projects so as to permit, by temporary deformation of such area, the sleeve to be driven along the prong so as to introduce the inner end of the sleeve and the outwardly projecting member into the housing during manufacturing assembly of the connector. It will further be appreciated that the temporary deformation required to permit the insertion of the inner end of the sleeve may occur in both the outwardly projecting member and in a corresponding area of the housing adjacent the opening.

Although reference has hereinbefore been made to the provision of resilient projections and areas, it will be appreciated that the required resiliencejor either or both of these structural parts may be obtained by forming these parts with appropriate dimensions, such as thickness. In this way, the several component parts may be formed as integral moulded structures permitting high speed manufacture and assembly ofthe connectors. The insulatingsleeve may, for xamplegbe formed as an integral moulded structure with the outwardly projecting member. This latter member may usefully take the form of an outwardlyidirected flange integrally formed .with lhe insulating sleeve at the inner end thereof.

Similarly, the resilient .area of the housing, if such is provided, may be formed as an integral part of the housing of the connector. Such resilience may be obtained for example, by the provision of an area of reduced thickness or by the provision of relatively resilient flanges integrally formed with the housing and surrounding the opening through which the electrode prong projects. i

The spring rneans serving to urge the insulating sleeve out of the housing will normally comprise a helically wound compression spring or ike resilient means acting on the innenend of the insulating sleeve or on the restraining means when the latter is connected to the insulating sleeve. To facilitate the manufacturing assembly operation, such compression springs. will normally be adapted to be slidingly inserted along the electrode prongs into the housings of the connectors.

In addition to providing an electrical connector of the type hereinbefore ,described, the present invention provides a method for the manufacture of such, connectors.

its broadest scope, the method of the invention comprises forming a housing with at least one electrode prong projecting therefrom through the opening in said housing, inserting a helically wour'id compression Spring slidingly surrounding said' prong into said housing, and finally inserting an insulating sleeve slidingly surrounding said prong along said prong so that an inner end of said sleeve enters into said housing, a resilient restraining means normally serving to prevent said inner end of said sleeve passing out of said housing being temporarily deformed during said inserting of said sleeve to permit said inner end of said sleeve to enter said housing.

During the manufacturing assembly of a connector according to the invention, the electrically-insulating sleeves will be inserted into the housing with a force sufficient to deform the resilient restraining means to permit the inner ends or the sleeves to enter the housing.

As previously stated, the present invention is particularly applicable to multi-pronged domestic electrical plugs. Such plugs are generally provided with electrode prongs which are substantially rectangular in cross-sectional shape. In a particularly useful construction for such a plug in accordance with the invention, both the insulating sleeves and the helically wound compression springs will have a substantially rectangular cross-sectional shape and the springs will be of such a size that they can be slidingly inserted along the electrode prongs into the housing passing through the spaces between the prongs and the housing.

DESCRIPTION OF THE DRAWINGS The invention will now be described merely by way of illustration with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of an electrical connector or plug in accordance with the invention at an early stage of its manufacturing assembly, with part of its housing cut away to reveal its internal structure;

FIG. 2 is a perspective view similar to that of FIG. 1 but at a later stage of the manufacturing assembly;

FIG. 3 is a perspective view similar to that of FIG. 2 after the manufacturing assembly has been completed and showing the insulating sleeves in their fully retracted positions; and

DESCRIPTION OF THE PIREFERRED 1' EMBODIMENTS The electrical connector shown in the drawings is a domestic two-prong plug. As hereinbefore stated," the present invention is generally applicable to connectors with one or more projecting electrode prongs but is of particular importance in its application to domesiic twoprong and three-prong plugs. '7

The plug shown in the drawings and indicatedgenerally therein at 10 comprises a housing 12 with two electrode prongs 14 and 16 secured therein and projecting therefrom. It will be noted that the prongs 14' and 16 extend into the rear of the housing 12 where they are connected to the exposed ends 18 and 20 of the conductor cord of wire 22 in a conventional manner, for example, by soldering. The prongs 14 and 16 are usefully provided at their rearward ends with transversely extending lugs 24 and 26 respectively to which the ends 18 and 20 are respectively connected. These lugs 24 and 26 serve to anchor or key the prongs 14 and 16 securely into the moulded lftOuSing 12. It will also be noted that, in the forward part of the housing 12, the prongs 14 and 16 are disposed within elongated passages 28 and 30 respectively. The forwardend of the housing 12 is provided with openings 34 and 36 communicating with passages 28 and 30 respectively and through "which the prongs 14 and 16 respectively project.

With further reference to FIG. 1, it will be seen that around'theSe openings 34 and 36, there are formed resilient lips 38 and 40 respectively. 1

Each of the prongs 14 and 16 is provided with an electrically-insulating sleeve 42, 44 respectively surrounding the prong and slidably mounted for movement between the retracted positions shown in FIG. 3 and extended positions as shown for sleeve 42 in FIG. 2.

The plug structure is Completed by helically wound compression springs 46 and 48 surrounding the prongs 14 and 16 respectively as will best be seen by reference to FIGS. 2 and 3. For a reason which will be more readily 'understood as the description proceeds, these springs 46 and 48 are dimensioned so as to be freely slidable along the prongs 14 and 16.

It will be seen that each of these sleeves 42 and 44 is provided at its inner end with an outwardly projecting flange 50, 52 respectively. When plug 10 is not inserted in a socket and when no pressure is applied to the outer bevelled ends 54 and 56 of sleeves 42 and 44 respectively, these sleeves are urged into their extended positions by the action of springs 46 and 48 respectively, the flanges 50 and 52 engaging the lips 38 and 40 respectively to prevent the sleeves passing completely out of the housing 12. The sleeves 42 and 44 preferably do not project in their extended positions as far from the housing 12 as do the electrode prongs 14 and 16.

When pressure is applied to the exposed ends 54 and 56 of the insulating sleeves 42 and 44 respectively, for instance, when the electrode prongs 14 and 16 are inserted into a mating socket as will be more fully explained hereinafter with reference to FIG. 4, the insulating sleeves 42 and 44 are driven into the housing 12 against the action of springs 46 and 48 to the position shown in FIG. 3.

It will be seen from FIG. 4 that, as the electrode prongs 14 and 1-6 are inserted into the corresponding openings 58 and 60 of the face plate 62 of an electrical socket, the outer ends 54 and 56 of the insulating sleeves 42 and 44 abut the face plate 62. As the plug is pushed to drive the prongs 14 and 16 into the socket to the position indicated at 62', the insulating sleeves 42 and 44 are forced into the housing 12 against the action of the springs 46 and 48.

Since those parts of the electrode prongs between the housing 12 and the face plate 62 of the socket are always covered by the insulating sleeves 42 and 44, danger of electrical shock or shorting of the electrical circuit by accidental contact with the prongs is substantially completely eliminated.

Referring again to FIGS. 1 to 3, it should be noted that, in the embodiment specifically illustrated, the outwardly extending flanges 50 and 52 formed at the inner ends of the sleeves 42 and 44 respectively are formed as integrally moulded structures with the sleeves. Similarly, the lips 38 and 40 are formed as integrally moulded structural parts of the housing 12.

Both the housing 12 and the sleeves 42 and 44 are formed of a thermo-plastic material and, by virtue of the relatively small thicknesses of the flanges 50 and 52 of the lips 38 and 40, these lips and flanges are sufliciently resilient, particularly immediately after moulding and before the plastic has set to its final hardness to be deformed or bent over during the manufacturing assembly of the plug so as in turn to permit the sleeves 42 and 44 to be driven along the prongs 14 and 16 respectively to introduce the flanges 50 and 52 into the housing 12. FIG. 2 shows sleeve 44 just prior to its flange 52 being driven through opening 36 into the housing 12.

Prior to the insertion of the sleeves 42 and 44 into the housing 12 during the manufacturing assembly of the plug 10, the springs 46 and 48 are slid along the prongs 14 and 16 respectively into the housing 12 as illustrated for spring 46 in FIG. 1. These springs are so dimensioned that they are capable of free movement both along the prongs 14 and 16 and through the openings 34 and 36.

Although the plug has been described as having both the flanges 50 and 52 and the lips 38 and 40 formed of a resilient material, it Will be appreciated that only one of these sets of structural component parts needs be formed so as to be resilient. For instance, the lips 38 and 40 may be resilient while the flanges 50 and 52 may be relatively rigid. In such a construction, introduction of the flanges 50 and 52 into the housing 12 during the assembly of the plug 10 will be effected substantially completely by the temporary deformation of the lips 38 and 40. Alternatively, the lips 38 and 40 may be relatively rigid and the required resilient may be provided in flanges 50 and 52.

The choice of appropriate materials for use in manufacturing the housing 12 and the sleeves 42 and 44 will depend on many factors such as the force to be used for inserting the sleeves 42 and 44 into the housing 12, the dimensions of the flanges 50 and 52 and the dimensions of the lips 38 and 40. Merely by way of illustration, it may be stated that a plug 10 has been constructed by an injection moulding technique from a polyvinyl chloride composition. The lips 38 and 40 were formed with a thickness of approximately 0.01 inch and with a transverse width of approximately 0.01 inch. The flanges 50 and 52 were formed with a thickness of approximately 0.05 inch and each extended outwardly from its sleeve a distance of approximately 0.03 inch. With such a construction, assembly of the plug was quickly and readily accomplished before the components set to their final hardness, i.e. within about two days of moulding. Once the sleeves 42 and 44 had been inserted into the housing, and the components had set to their final hardness, the flanges 50 and 52 and the lips 38 and 40 were found to be sufliciently strong to retain the inner ends of the sleeves within the housing during normal use of the plug.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. An electrical connector comprising a housing with at least one electrode prong projecting therefrom, an electrically-insulating sleeve surrounding and slidably mounted on said prong, having an inner end and an outer end and adapted to be displaced into said housing by the application of pressure to said outer end of said sleeve, spring means disposed within said housing and acting on said sleeve to urge said sleeve out of said housing along said prong, and restraining means normally serving to prevent said inner end of said sleeve passing out of said housing but said restraining means being sufliciently resilient to permit said sleeve to be driven along said prong to introduce said inner end of said sleeve into said housing during manufacturing assembly of said connector.

2. An electrical connector as claimed in claim 1 in which said housing is provided with an opening through which said electrode prong and said insulating sleeve project and in which said inner end of said sleeve is normally prevented from passing out of said housing by engagement of an outwardly projecting member secured to said sleeve at or in proximity to its inner end with said housing.

3. An electrical connector as claimed in claim 2 in which said outwardly projecting member is resilient so as, in turn, to permit, by the temporary deformation of said outwardly projecting member, said sleeve to be driven along said prong to introduce said inner end of said sleeve and said outwardly projecting member into said housing during. manufacturing assembly of said connector.

4. An electrical connector as claimed in claim 2 in which said housing is formed so as to be resilient in an area adjacent said opening so as, in turn, to permit, by temporary deformation of said area, said sleeve to be driven along said prong to introduce said inner end of said sleeve and said outwardly projecting member into said housing during manufacturing assembly of said connector.

5. An electrical connector as claimed in claim 2 in which said outwardly projecting member is an outwardly directed flange integrally formed with said insulating sleeve at said inner end thereof.

6. An electrical connector as claimed in claim 5 in which said spring means comprises a helically wound compression spring surrounding said electrode prong within said housing and acting on said inner end of said sleeve, said compression spring being adapted to be slidingly inserted into said housing along said electrode prong during manufacturing assembly of said connector.

7. An electrical connector as claimed in claim 6 in which said insulating sleeve and said outwardly directed flange comprise a unitary moulded structure.

8. An electrical connector as claimed in claim 7 in which said electrode prong, said opening in said housing, said insulating sleeve and said helically wound compression spring each has a substantially rectangular crosssectional shape and in which said helically wound compression spring is so dimensioned as to permit its free passage along said electrode prong through said opening into said housing during manufacturing assembly of said connector.

9. A method of manufacturing an electrical connector which comprises forming a housing with at least one electrode prong projecting therefrom through an opening in said housing, inserting a helically wound compression spring slidingly surrounding said prong into said housing, and finally inserting an insulating sleeve slidingly surrounding said prong along said prong so that an inner end of said sleeve enters into said housing, a resilient restraining means normally serving to prevent said inner end of said sleeve passing out of said housing being temporarily deformed during said inserting of said sleeve to permit said inner end of said sleeve to enter said housing.

10. A method as claimed in claim 9 in which said housing is formed by a moulding operation from a thermoplastic and electrically-insulating composition to have an opening with said electrode prong projecting therethrough and in which said inner end of said sleeve is inserted along said prong through said opening into said housing so that an outwardly directed resilient projection formed at or in proximity to said inner end of said sleeve is temporarily deformed to permit said projection to enter said housing and there to be urged by said helically wound compression spring normally to engage said housing to prevent said inner end of said sleeve passing out of said housing.

11. A method as claimed in claim- 9 in which said housing is formed by a moulding operation from a thermoplastic and electrically-insulating composition to have an opening with said electrode prong projecting therethrough, said housing being formed in an area adjacent said opening so as to be resilient so as, in turn, to permit, by its temporary deformation, an outwardly directed projection formed at or in proximity to said inner end of said insulating sleeve to be inserted into said housing and there to be urged by said helically wound compression spring normally to engage said housing to prevent said inner end of said sleeve passing out of said housing.

References Cited FOREIGN PATENTS 1/ 1909 Germany. 11/ 1966 Switzerland.

MARVIN A. CHAMPION, Primary Examiner J. H. MCGLYNN, Assistant Examiner U.S. Cl. X.R. 29529 

